The present invention relates to a chamber having a gas feed-through for introducing gas into the chamber.
In the fabrication of electronic devices, semiconductor, dielectric and conductor materials, such as for example, polysilicon, silicon dioxide, and metal containing layers, are deposited on a substrate and etched to form features such as patterns of gates, vias, contact holes and interconnect lines. These features are typically formed by chemical vapor deposition (CVD), physical vapor deposition (PVD), oxidation and etching processes. For example, in a typical etching process, a patterned mask of photoresist or oxide hard mask is formed on a deposited layer by photolithographic methods and exposed portions of the deposited layer are etched by an energized halogen gas, such as Cl2, HBr, and BCl3. In a typical CVD process, a gas provided in the chamber is decomposed to deposit a layer on the substrate. In PVD processes, a target facing the substrate is sputtered to deposit the target material onto the substrate.
In these processes, gas is supplied to the chamber through a gas feed-through. For example, the gas feed-through can be used to feed process gas into the chamber for processing of the substrate. The gas feed-through can also be used to feed gas to a surface of a support below the substrate, the gas being useful for enhancing heat transfer rates to and from the substrate, and for reducing deposition of byproducts on the backside or edges of the substrate. However, when an electrode in the chamber is electrically biased, for example, to energize a plasma in the chamber or generate electrostatic forces, the electric potential applied to the electrode can cause plasma formation, arcing, and glow discharge in the gas passing through the gas feed-through. Such arcing and glow discharges damage the gas feed-through and adjacent chamber components or surfaces. Arcing can also cause catastrophic failure of the gas feed-through upon plasma ignition; randomness (or wide error band) of breakdown voltage across a large substrate; sensitivity of breakdown voltage to material imperfections, voids, and gaps at interfaces within the gas feed-through; and cause the applied voltage at which an ignited gas in the gas feed-through is extinguished to be more than an order of magnitude smaller than the voltage at which it is ignited. All these effects impede the efficient processing of substrates or other workpieces in the chamber.
Commonly assigned U.S. patent application Ser. No. 08/965,690, filed on Nov. 6, 1997, entitled xe2x80x9cElectrostatic Chuck Having Improved Gas Conduitsxe2x80x9d to Weldon, et al., which is incorporated herein by reference, describes a ceramic insert that is positioned in a conduit in a ceramic electrostatic chuck (which has an electrode that is charged to electrostatically hold an overlying substrate) to reduce plasma formation in the conduit. While this device reduces plasma formation in the conduit it has been observed that plasma formation still often results in the conduit when the voltage applied to the electrode exceeds certain levels. In addition, instantaneous changes in electrical potential can ionize the gas adjacent to the gas feed-through, particularly when the diameter of the conduit is relatively large and provides a long mean free path that leads to avalanche breakdown of gas molecules in the conduit. For example, arcing has been occasionally observed at voltages of about 2 KVp and at high frequencies of 13.56 MHz.
Thus there is a need for a gas feed-though that reduces plasma formation, glow discharges and arcing, during passage of gas through the feed-through. There is also a need for a chamber that can process a substrate in a gas while reducing the incidence of plasma formation of gas in conduits that feed gas into the chamber. There is a further need for a method of providing gas to a chamber while simultaneously reducing the incidence of plasma formation in the feed-through.
In one aspect, the present invention relates to a gas feed-through that provides gas to a chamber, the gas feed-through comprises a dielectric insert having a passage that allows the gas to be flowed therethrough, and a electrically conducting cup around a portion of the passage. The electrically conducting cup is shaped to reduce plasma formation in the gas feed-through during the passage of gas in the feed-through into a chamber.
In another aspect, the present invention comprises an substrate support assembly comprising a dielectric layer covering an electrode that may be charged with an RF voltage; and a gas feed-through comprising a dielectric insert having a passage through which gas may be passed to the surface of the dielectric layer, and a electrically conducting cup around a portion of the passage.
In yet another aspect, the present invention comprises a chamber capable of processing a substrate in a plasma, the chamber comprising a gas feed-through comprising a dielectric insert having a passage through which a gas may be passed into the chamber, and a electrically conducting cup around at least a portion of the passage.
In still another aspect, the present invention comprises a method of processing a substrate in a chamber, the method comprising the step of passing a gas through a passage in a dielectric insert of a gas feed-through, and maintaining a electrically conducting cup around a portion of the passage to reduce an incidence of plasma formation in the passage.